If you like antique engines, vintage tractors or old iron, please register and join us. When you register and log in, lots more features open up to your computer screen. Give us a try and register. See our Welcome Page!

Hi Mark,
Shoot off a PM to Scotty 2 on this site. He lives in Warwick as well and has a good understanding of magnetos. Not sure when he will be back at Warwick but I think it is soon.
He has been very patient trying to get me to understand all the readings on my multimeter but it sounds like you need a mechanical fix info, he just might be the man.

First let me say I don't know anything about that type of magneto. Now, what are the bearing insulators insulating? The only thing that comes to my mind is a bearing shim made of paper or similar to hold the bearing tight in the casting? No bearings I've ever seen or heard of on a magneto are made to be in contact with electrical current. If you're talking about magnetism then a similar principle would apply. Magnetism is insulated by distance not material. I would think if you magnetized a bearing it would prematurely fail although I have not tried it. Hope this helps. If I'm on the wrong track, maybe you can clarify a little about what you're describing and get more direct answers. Hope this helps.

Thanks mmcdonald,
As i'm just the novice, I've seen some magneto bearings with paper (what I thought was insulators) but from what you said the paper is only to take up the slack and make it firm, so I think it would be fine to put the new outer bearing racers in with out the paper shims as it is a well machined fit.
The magneto came of of my French made J Fivet 4hp.
Many thanks Mark

Hello Mark.
A way of seeing if they have not have had an insulating washer is to get the trusty multimeter, put it on ohms and put one probe on the shaft and the other probe on the spot where the bonding or earthing brush runs. If there is a circuit then an insulating washer is needed. If no circuit then an insulating washer may not have been used. Emphasis in may not.